Undocumented Google Calendar URL Parameter #1

While doing some looking into ColdFusion components and research into RFC 5545, Google Calendars, and Yahoo! Calendars, I did some experimenting to see how much I can specify for a calendar event via URL in Google Calendars. I quickly found the action, text, desc, dates, and location parameters. Some additional looking found the sprop and trp parameters.

I opened up a new calendar event and tried to find ways to specify other portions of the form through URL parameters. I eventually found that I could use the recur parameter and specify a full RDATE or RRULE property and value string in URL-encoded format. For instance, if you wanted to create an event that repeated monthly on the second Sunday, you could add:

recur=RRULE%3AFREQ%3DMONTHLY%3BWKST=SU%3BBYDAY%3D2SU

to the URL. That's a URL-encoded form of the following.

RRULE:FREQ=MONTHLY;WKST=SU;BYDAY=2SU

I didn't find this documentation anywhere else, so I'm posting it here for someone else to find.

I'm still looking for ways to specify reminders and attendees. If you know how to do either of these, let me know.